Conical flanges are commonly used to stiffen sheet material in which relatively large circular openings are formed. By way of example, rib and spar members in aircraft frames are often made from sheet aluminum, and large circular "lightening holes" are provided to both lighten the members and provide passageways for control cables, hoses and the like. Conical flanges are formed about the periphery of the openings in order to stiffen the members.
Specialized heavy machinery is used in large-scale manufacturing environments to form the desired conical flanges in sheet material. For example, special fixed-dimension dies may be used in conjunction with a stamping operation to form conical flanges in an efficient and economical manner when relatively numerous operations are contemplated. The need has arisen, however, for a small hand-operated tool for forming conical flanges in small numbers and without specialized, heavy equipment. Such a tool would be useful, for example, in the repairing of aircraft where a single or small number of ribs or spars are to be fabricated at the repair facility. The flange-forming tool should be operable by hand to form a conical flange in a malleable sheet material, and the tool should be adjustable to accommodate openings of varying size and flanges of varying widths, thicknesses and angular displacements, depending on the application.